The Delaware conundrum, Part Five

As I discussed here, the Tea Party Express released a poll last week showing that conservative Christine O’Donnell trails moderate Mike Castle in the Delaware Republican Senate primary by only 6 points among likely voters. The poll also shows that O’Donnell is only 2 points behind Rep. Castle among those most likely to vote.
Is O’Donnell really that close? On the one hand, the Tea Party Express polling that showed Joe Miller closing in on Lisa Murkowski in the Alaska Republican Senate primary proved to be spot on. On the other hand, this Delaware poll had a sample size of only 300, with a resulting margin of error of nearly 6 points. In addition, the poll was taken before O’Donnell gave a well-publicized and rather problematic interview on a popular Delaware radio talk show. And recently, Castle (not wanting to suffer Murkowski’s fate) has been attacking O’Donnell, after having previously ignored her.
Finally, Castle’s pollster, Jan van Lohuizen (for whom my daughter works) told the Washington Post’s Chris Cillizza that “the primary is in good shape, and this won’t be another Utah or Alaska.” Van Lohuizen was President Bush’s pollster and I don’t think he would be putting his reputation on the line if he didn’t have solid polling data that shows Castle in command of the race.
My guess is that Castle has the votes to win the primary. But he had better make sure his voters show up for the election on September 14, because O’Donnell may now be in a position to win a low turnout primary.